Ms Robinson, who rents Ms Down's granny flat with her partner and has a background in horticulture, saw the plants were not thriving and provided advice on how to better water and fertilise them.

Lawyer Shash Nigam said Ms Down believed her son suffered whenever he was admitted to psychiatric facilities, including Graylands Hospital, so she cared for him at home.

He told the court Ms Down's caring responsibilities had a "ruinous effect" on her life, preventing her from attending church or engaging with friends, and even causing her to miss her brother's funeral.

"All her energy and all her time is spent managing her son," Mr Nigam said.

Judge Stewart said the number of cannabis plants was "not insignificant", but accepted Ms Down had cultivated them purely for medicinal use.

However, she said the pensioner should not have attempted to help her son by supplying him with cannabis.

"His psychiatrist, not you or anyone else, is in charge of his mental health," she said.

Judge Stewart acknowledged Ms Down's financial situation was "not good" and she would not be able to pay a fine.

The pensioner received a 25 per cent reduction on her sentence for her guilty plea and cooperation with police.

Cannabis makes way for flowers and vegies

After her sentence was read out, Ms Down told the court she would never grow cannabis again.

"I've got flowers and vegetables out there now," she said.

Speaking outside court, Ms Down said she was "happy".

"I think the judge was very fair. I hate drug traffickers," she said.

Ms Down, a widow with three sons, retired when she was 48 and became a carer for her mother-in-law, mother and husband.

She said her son, who is now in rehabilitation, had been violent before the cannabis use, smashing up her house and throwing food around.

"After a while, you get desperate," she said.

Ms Down still faces the prospect of losing her house under the Criminal Property Confiscation Act.

Her lawyer, Mr Nigam, said he expected to hear from the Director of Public Prosecutions on the matter next year.